Has anyone had any experience with a product called Deck Armor by GAF? I have a school project that has this specified in lieu of felt paper under the shingles. Problem is, in the submittal information, they call it "breathable" which to me translates "it leaks". It has to go over a fire rated UL assembly of metal deck, 5/8 rated drywall, 5/8 plywood. If it leaks the drywall turns to mush. Will the roofer have to keep everything tarped until the shingles are on? I can't even get a straight answer out of the GAF rep.